: The long-term goal of this research is to understand the organization of complex sound processing in the human lateral temporal lobe. We will focus on temporal lobe processing of complex frequency-modulated (FM) sounds, including speech. The ability to discriminate FM sounds that differ in rate and direction of frequency change is integral to many auditory behaviors, including speech perception. The main hypothesis motivating this research is that a subsystem within the lateral temporal lobe is specialized for discriminating complex FM sounds. It is further hypothesized that absence of functional specialization is associated with auditory processing abnormalities. We will test these hypotheses by combining functional lesion (cortical stimulation) and neurophysiologic (electrocorticography) methods with an auditory discrimination paradigm, to study seizure patients with electrodes implanted subdurally for clinical purposes. Preliminary studies have confirmed the feasibility of the methodologies proposed.The specific aims are to: 1) delineate lateral temporal lobe regions that are critical for complex FM sound discrimination; 2) quantify variability in the temporal lobe representations of complex FM sound discrimination in normal and abnormal central auditory systems; and 3) identify spatial and temporal features of electrocorticographic responses that suggest specialization for complex FM sound processing. The significance of this research includes a better understanding of the functional organization of the lateral temporal lobe system and the associated effects of variability. Of methodological importance is the opportunity to correlate complementary cortical mapping techniques. Clinical implications include elucidating the relationship between temporal lobe representations of complex sound processing and individual auditory processing abilities.